mesa 0d88b15f073d09afed1747d9cdde98f15c7aa28d regressed this test:

Standard Output

/tmp/build_root/m64/lib/piglit/bin/shader_runner /tmp/build_root/m64/lib/piglit/tests/spec/arb_separate_shader_objects/execution/layout-location-named-block.shader_test -auto
piglit: debug: Requested an OpenGL 3.2 Core Context, and received a matching 3.3 context

Standard Error

Failed to link:
error: fragment shader input `name2' with explicit location has no matching output
error: fragment shader input `name' with explicit location has no matching output

------------------------------------------------------------
Author:     Timothy Arceri <timothy.arceri@collabora.com>
glsl: cross validate varyings with a component qualifier

This change checks for component overlap, including handling overlap of
locations and components by doubles. Previously there was no validation
for assigning explicit locations to a location used by the second half
of a double.

V3: simplify handling of doubles and fix double component aliasing
detection

V2: fix component matching for matricies

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>